There has been considerable demand for light-duty liquid or gel dishwashing detergents capable of providing good grease removal. These compositions are well known in the art and are described, for example, in U.S. Pat. Nos. 4,316,824 (Pancheri), 4,4,681,704 (Bernardino et al.), 4,133,779 (Hellyer et al.), and 4,615,819 (Leng et al). These compositions, although being good grease and soil cleaners, can be harsh to the skin under certain conditions, particularly when used during the dry winter months.
Likewise, the art is replete with detergent compositions that are mild to the skin. These mild compositions often contain sulfates of highly ethoxylated alcohols. See, for example, U.S. Pat. No. 3,743,233, Rose and Thiele. Betaines have also been suggested for use in improving mildness of a liquid dishwashing composition. See, for example, U.S. Pat. No. 4,555,360 (Bissett et al). Alkyl ethoxy carboxylates are also known as mild surfactants for use in liquid detergent compositions. See Japanese Patent Applications 48-60706 and 48-64102. These alkyl ethoxy carboxylate surfactants, however, have been described as being poor in their grease cutting ability and require the use of other surfactants to achieve the desired cleaning.
Rarely have these two important features of mildness and grease cutting ability been incorporated in one product. It is generally thought that one must be sacrificed for the benefit of the other. It has been discovered that detergent compositions containing a particular alkyl ethoxy carboxylate surfactant mixture provide a detergent composition that exhibits good grease removal while manifesting mildness to the skin. This dual benefit is enhanced when the composition has a pH of from about 7 to 11 and contain a small amount of divalent ions, e.g. magnesium.
These alkaline compositions containing magnesium ions may exhibit poor stability during storage though. In an alkaline environment, the precipitation of magnesium hydroxide can be a substantial problem. Therefore, it is an object of this invention to provide a detergent composition that exhibits good grease removal and mildness to the skin while providing superior stability during storage of the composition.